Antiperspirants combat axillary odors by inhibiting perspiration through the action of astringent salts such as aluminum and zinc salts, but may be irritating to a considerable number of users. On the other hand, deodorants neutralize the objectionable odors resulting from the degradation of the components of sweat due to chemical and microbial attack into malodorous fatty acids. Deodorants do not inhibit sweating but rather neutralize the malodorous degradation products of sweat, either by their own odorous properties, or by the inhibition of the decomposition action of microbial action on the fats in the sweat residues, or by reaction with the malodorous fatty acids or by any combination of these mechanisms.
Numerous stick antiperspirant compositions are known in the art. Those skilled in the art have found that anhydrous antiperspirant stick systems are more advantageous to market and have good consumer acceptance primarily due to the ease of application to the skin, good cosmetic aesthetics and an acceptable degree of effectiveness. Previous to the development of anhydrous stick systems, numerous water based systems were developed in which the active astringent salts were solubilized in a thickened or gelled composition. This is exemplified in U.S. Pat. Nos. 2,732,327, 2,857,315, 3,255,082, and 3,928,557. The water based systems are difficult to apply to the skin and their consistency and effectiveness are questionable.
Many anhydrous stick compositions have been described in the literature which attempt to improve the delivery and the effectiveness of their antiperspirant and deodorant characteristics. For example, antiperspirant stick systems consisting of low molecular weight monohydric alcohols in conjunction with polyhydric alcohols, as described in U.S. Pat. No. 4,137,306 have the advantage of quicker drying rates, but the residue of the polyhydric alcohols in combination with the astringent salts produces a high degree of tack and their effectiveness is limited to the type and amount of astringent salts that could be incorporated therein.
Anhydrous stick compositions that suspend the aluminum salt in a hydrophobic matrix, as described in U.S. Pat. No. 4,049,792, make use of waxy materials and long chain fatty esters to form a stick that delivers the active astringent salts to the skin. Preparations made by these teachings are rather greasy and they envelop the active astringent salt for long periods of time preventing their maximum performance. To alleviate this inherent negative characteristic, volatile silicone fluids replaced the lesser volatile long chain fatty esters as described by U.S. Pat. No. 4,126,679. This patent teaches the advantage of incorporating a volatile, non-staining liquid such as cyclic dimethylpolysiloxanes, referred to as volatile silicones, in combination with various types of waxes as a carrier for the active astringent salts in an antiperspirant stick composition. Similar antiperspirant stick compositions containing volatile silicones are described in U.S. Pat. Nos. 4,511,554, 4,980,156 and 4,985,238.
Although the volatile silicone based antiperspirant stick compositions are effective and highly aesthetic, they may contain up to 80% by weight of volatile silicone. While the use of such large amounts of volatile silicone make preparations thusly prepared more stable, they may be brittle and hard and, more importantly, they tend to leave an unsightly white chalky residue on the skin after application. This residue is not only aesthetically displeasing to the user, but can also soil clothing. In an effort to alleviate this problem, U.S. Pat. No. 4,985,238 discloses that when certain non-volatile paraffinic hydrocarbon fluids, such as mineral oils or branched chain C.sub.16 -C.sub.68 hydrocarbons, are incorporated into water-free suspensoid antiperspirant stick compositions, these compositions exhibit antiperspirant efficacy and aesthetics, while leaving reduced visible residue on the skin of the user.
The compositions of U.S. Pat. No. 4,985,238 or any of the related art, however, do not contemplate the use of relatively large amounts of a deodorant active material, such as a carbonate or a bicarbonate, in conjunction with the active astringent salts.
Sodium bicarbonate has long been recognized for its deodorant properties, and has commonly been used as a household deodorant. Plain powdered sodium bicarbonate or sodium bicarbonate diluted with talc, cornstarch, rice-flour, or other filler has been used as an underarm deodorant as disclosed in U.S. Pat. No. 4,382,079.
However, the development of a practical and effective antiperspirant composition in stick form which is also capable of deodorization and, which is capable of consumer acceptability, presents many considerations which are unique. Because sodium and potassium bicarbonate have only limited solubility in water, alcohol and other solvents, the preparation of a composition suitable for dispensing in stick form has been an exceedingly difficult and perplexing problem. In addition to the problem of limited solubility of the sodium bicarbonate; its incompatibility with the active astringent salts and with other ingredients of conventional stick compositions; the dimensional stability of the stick containing sodium bicarbonate; its aesthetic appearance and its "feel" on the skin, are just a few of the additional problems encountered in the preparation of a low residue antiperspirant/deodorant stick.
While antiperspirant sticks are old, as evidenced by the above patents, none of these publications suggests the criticality of the specific combination of components described by the present invention. This combination of components gives antiperspirant sticks which are both highly efficacious and cosmetically pleasing.
It is therefore an object of the present invention to provide cosmetic sticks which have excellent cosmetic properties (e.g., ease of application to skin, "glide", a low visible residue) and are easy to manufacture. A further object of the present invention is to provide cosmetic sticks which very effectively deliver water-soluble active materials, particularly deodorant and/or antiperspirant active materials, to the skin. A still further object of the present invention is to provide cosmetic compositions which feel dry; do not feel greasy or gritty; go on cleanly and evenly; remain evenly dispersed with no visible cakey, chalky residue after application; and appear uniformly opaque and non-gritty. An object of the present invention is also to provide methods for treating or preventing malodor associated with human perspiration, especially underarm odor.
It has been surprisingly discovered that the above objectives can be realized by formulating a stick comprising the ingredients described hereinafter.